RFR: 8333583: Crypto-XDH.generateSecret regression after JDK-8329538 [v3]

[Anthony Scarpino]

On Mon, 17 Jun 2024 18:51:33 GMT, Volodymyr Paprotski <duke at openjdk.org> wrote:

>> What causes regression in P256 "(~-8-14%)"?
>> From what I see, you re-arranged code to not execute some code ("reducePositive()") when it is not needed. How this affects P256?
>
>> What causes regression in P256 "(~-8-14%)"? From what I see, you re-arranged code to not execute some code ("reducePositive()") when it is not needed. How this affects P256?
> 
> Actually, the other way around; reducePositive is now an unconditionally executed for both pure java and the intrinsic paths. Perhaps that's what is misleading, it was only the mult() intrinsic that was taking advantage of this 'skip reduction' before. (pure java did not benefit from removing reduction, so I kept it. Now 'keeping it' for both paths)

Hi @vpaprotsk, 
@ferakocz is going to take a look at the change.  When he says it's ok, I'll approve the PR.

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PR Comment: https://git.openjdk.org/jdk/pull/19728#issuecomment-2174249460